1. Technical Field
This disclosure relates to an image forming apparatus, and more specifically to an image forming apparatus including a recording head for ejecting liquid droplets.
2. Description of the Related Art
Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. As one type of image forming apparatus employing a liquid-ejection recording method, an inkjet recording apparatus is known that uses a recording head (liquid-droplet ejection head) for ejecting droplets of ink.
When image formation is performed with such a liquid-ejection type image forming apparatus, the landing accuracy of liquid droplets ejected from nozzles significantly affects image quality. As a low level of landing accuracy reduces image quality, it is preferably to position the recording head at high accuracy.
For this reason, when a plurality of recording heads are mounted on a plurality of head holders, the relative positions of the recording heads mounted on the head holders need be determined at high accuracy.
Hence, for example, JP-02-001327 proposes an image forming apparatus that moves carriages mounting separatable head holders along guide rods parallel to each other. The head holders have a pressing member and a locking mechanism to position the head holders in the main scanning direction when the head holder are connected.
However, for the configuration proposed in JP-02-001327, since a connecting mechanism is disposed at the head holders, accumulated errors may occur. In addition, using the lock mechanism causes a complex configuration and increased cost.
In addition, if ejection failure occurs in the recording head, it is preferable that the recording head can be easily replaced at the site at which the apparatus is used. Even in such a case, a high degree of positioning accuracy of the recording head need be reproduced after replacement.
To enhance the positioning accuracy in replacing the recording head, for example, JP-2011-037235-A1 proposes an image forming apparatus including a head holder mounting liquid ejection heads and a carriage removably mounting the head holder. The head holder has positioning portions to contact positioning references in both the carriage scanning direction and the sheet conveyance direction, and the positioning portions serve as positioning references relative to the head holder of liquid ejection head.
However, for the image forming apparatus disclosed in JP-2011-037235-A1, the carriage of the head holder is positioned by positioning faces and pins, thus resulting in a complex configuration. In particular, in a case where the image forming apparatus has multiple head holders, the positioning portions need be provided for the respective head holders. Such a configuration makes it difficult to position the head holders relative to each other at high accuracy and replace the recording head in a simple manner.